Thanks for testing this further, in that case, it does point further to the network as well.
Personally I have a TP-Link unmanaged switch and it works well, but if you want to read what other users have, there are a few threads on the forum, for example:
If you purchase a Nucleus, you would still need to place it on a properly functioning network. My suggestion here is to replace the switches first, verify how the setup performs and then look into purchasing a Nucleus, that way you know the network is operational.
The difference between these two units is listed on our website (towards the bottom):
https://roonlabs.com/nucleus
It is primarily regarding library size and amount of zones in use at a time.